Superresilient wheel



A rilfl, 1942. EH IRON 2,278,712

SUPER RESILIENT WHEEL Filed Nov. 29, 1940 1 /////Ad0 Y T 2 7 I x,

i 0 1 X g /1 /7 4X) I m 1/ a 1\\/'ENTOR.

ATTORNEY.

Patented Apr. 7, 1942' I surnaaasnaau'r WHEEL Emil n. Piron, new York,N. 1., assignor to Transit Research Corporation, New York, N. Y,, acorporation of New York Application November 29 1940, Serial No. 367,826

6Claims.

This invention relates to resilient wheels adapted for use on rails, ofthe particular type wherein elastic elements of rubber Or similarmaterial are stressed in shear by relative radial movements of the tireand hub.

-Wheels of this general type are coming into wide usage particularly forstreet cars where the problem 01' quietness i highly important. All suchwheels, to date, are equipped with comparatively thin rubber elements ofsubstantial hardness in order to keep'well within safe operating limits.Long experimentation has now revealed the manner of constructing thesewheels and of selecting rubber springing elements therefor such that amaterial improvement in sound deadening and in riding quality results.The obiect of this invention is to reveal the manner inwhich theseimproved results are attained.

More specifically it is an object of this invention to provide springingelements of optimum size, thickness, durometer hardness and shape toaccomplish the above objects and, further, to provide a peripheral shapewhich will safeguard the elements against surface cracks anddeterioration which readily spread through the interior thereof.

Resilient rail vehicle wheels of the type here concerned comprise huband tire plates, connected to the tire and hub of the wheelrespectively, and connected together by elastic springing elements insuch manner that the plates may move relatively. The elastic elementsare formed of rubber, or its equivalent, and act in radial shear toresist radial forces and in torsional shear to resist torsional forcessuch as result from driving or braking. It has been found necessary, forpractical reasons, to groove the inner and outer peripheral edges of theelastic elements, because the elastic elements are maintained undercompression by the plates to which they are connected. If the groovingis omitted, compression of the elastic elements causes the peripheral orcontour edges to bulge, and bulging of the elements places the rubber atthe contour edges untionalarea unnecessarily reduced, but folding of therubber appears at the bottom ofthe groove,

and causesthe rubber to gum and destroy itself. Both of theseconditions, tension and folding, may be present at the same time if thecontour of the groove is not correct, with the result that cracking mayappear in one region and gumming in another.

The main object of this invention is to teach the formation of a groovewhich is correctly proportioned and shaped to eliminate the destructiveconditions above noted. I

Other objects and advantages will become more fully apparent asreference is had to the accompanying drawing wherein m'y invention isillustrated, and in which 7 I Fig. l is a transverse diametric crosssection of a wheel with the springing element i'ully compressed,

Fig. 2 is an elevation of an elastic spring, with a small portionthereof broken'away and in cross section, v

Fig. 3 is a diagram illustrating the curvature of the grooves in theelastic spring, and.

Fig. 4 is a transverse section taken along the lined-401F582.

More particularly, 8 designates a wheel hub having a main radial plate 2welded or otherwise fixedly secured'thereto. A conical brace plate 3extends from the hub to an attaching point or attaching circle near theperiphery of the main plate 2. This plate I, together with an-outwardly,fiared flange portion 4,,rlgidifies the main plate 2.

A sleeve 5 fits onto the hub I and carries a second main plate 6, whichextends-radially therefrom. As the sleeve -5'and its plate 6 is slidonto the hub I, it imposes compression on two elastic der tensionstresses which cause cracks to develop in the elements.

The grooving, however, in order to be eflicient, must have certaincharacteristics which, if not respected, result in different troubles.For example, if the depth of the grooveis not properly related to thewidth of the element, an amount of springing elements I which support atire carrying plate 8. A rail contacting tire 9 is integrally connectedto the plate 8.

Each of the elastic springing elements I has two metallic discs to ofsome suitable thin material the surface of which is bonded thereto andboth discs IQ of an element are dowelled at H to respective main platesand to the tire carrying plate 8. A nut l2, on the hub I, maintains thesleeve 5 with its plate 6 compressing the elastic springs 1 so thatrelative radial movements between the tire plate 8 and the hub plates 2and t are sustained by the elements I, acting in shear.

Lateral forces between'the tire 9 and hub i will, of course, tend tospring the plate 6 outwardly, andto prevent this action the platev 8 isconnected to the plates 2 and 3 by a multiplicity of bolts I3 havingspacer shoulders ll thereon. The bolts ll extend through recesses orscallops l 5 in the springing elements 1. and through openings IS in thetire carrying plate 8. The recesses or scallops I! in the elasticelements 1 comprise a series of peripheral, U-shaped radially disposedcut out portions.

The above described wheel construction is intended to generallyrepresent any of the many conventional as well as specially designedresilient rail vehicle wheels, wherein elastic shear springs, commonlycalled rubber or elastic sandwiches, are maintained in compression andact in shear to support the rim or tire with respect to the hub. It hasbeen found, in service, that compression of the springs is essential.Compression, however, ordinarily causes the contour edges of the springto bulge, which places such edges under tension stresses whichultimately cause cracks to develop in the rubber. This problem hasibeenrecognized heretofore and the solution proposed teaches the grooving ofthe contour edges of the elastic springs.

If the contour edges of the springs are grooved, however, the grooves.in order to be eflicient, must have certain proportions andcharacteristics which if not respected result in the development 0!further troubles. For example, it the grooves are not sumcently deep, acertain amount of bulging still appears in the compressed condition, andsubsequent cracking of the rubber is not avoided. If the grooves aremade too deep, the working sectional area of the spring is unnecessarilyreduced, and in addition, folding of the rubber appears at the bottom ofthe groove I and causes the rubber to gum and destroy itself.

The cross sectional shape of the groove also is an importantconsideration, for the reason that ii the contour is not correct, andwithin certain limits, folding or tension may appear in differentlocations, sometimes individually and sometimes slmultaneo ly. Either orboth or these conditions is followed by gumming or sell destruction.

scallops l5, are grooved in themanner indicated at H in Figs. 2 and3,'and the groove has a; particular cross sectional shapediagrammatically shown more clearly in Fig, 3. This groove, as shown inFig. 3, has a shape which follows the general equation of a parabola,which is r'=ay, Where the X-axis is a tangent to' the bottom of thegroove, and where the axis Y passes through the pointoi contact betweenthe axis X and the bottom of the groove. The parameter a or the parabolamust have a value given in inches by a=0.0852r+0.58, where r is theradius of the contour edge of the sandwich, at the point where the crosssection of the groove is considered.

The depth of the groove, or y dimension at the bottom or the grooveaccording to the dIagram is given by the relation when 2: equals onehalf or the thickness of free rubber, 1! equals the height of-thecontour of the groove above the X axis tangent to the bottom of thegroove, which value. in this particular case,

is equal to the depth of the groove. In the diagram, the sign :1represents the particular value 01 :r'equal to half the thickness of thefree rubber,

and 111 represents the corresponding 1 The-depth by ill-1!.

Taking for example,.a rubber sandwich 1.46

inches thick, having an outer radius or 10 inches. an inner radius of4.25 inches at the center hole, and an inner radius of 1.25 inches atthe scallops I 6. Then, it

and it The rest 0! the contour of the groove is given respectively by Inpractice, the contour oi the grooves will vary somewhat from thespecific proportions given do not materially impair the i'unction oithe.

groove unless such variations are excessive. Experience has proven thatfor a given value of K, a variation of plus or minus 20% may besatisfactory. but the variation must, of course, be maintained as low aspossible, for a variation even within this range is liable to start someincipient folding in the rubber.

Although a specific embodiment of the invention has been illustrated anddescribed, it will be understood that various changes may be made withinthe. scope of the appended claims without departing from the spirit 0!the invention and such changes are contemplated.

What is claimed is:

1. A shear spring. comprising a disc of elastic plastic material adaptedto be compressed when placed in' service, said spring having acircumferentially extending groove in its peripheral edge, said groovehaving a cross sectional-contour corresponding to the shape oi aparabola when.

said disc is free from compression, with the contour of the parabolafollowing within approximately 20% plus or minus the equation where z isthe abscissae measured from the median axis of the groove, where aequals 0.08521 plus 0.588 with r being the radius of the grooved edge atthe point where the contour of the groove is being considered, and 11serves to determine the depth 0! the groove for any value of x.

2. A shear spring comprising a disc of elastic plastic material adaptedto be compressed when placed in service, said spring having acircumferentiallyextending groove in its peripheral edge, said groovehaving a cross sectional contour corresponding to the shape of aparabola when said disc is free from compression, with the'depth ofthegroove given within approximately 20% plus or minus by the relationwhere 1/: equals the depth of the groove, :1 equals one hall the widthof the groove, and a equals axially therethrough. the wall of saidopening,

having a groove extending 'circumierentially therearound, said groovehaving a cross sectional shape of a parabola following within plus oraxis of the groove, where :1 equals 0.08521 plus 0.588 with 1' being theradius of the opening at the point where the shape of the groove isconsidered, and 1/ determines the shape of the. groove. 4. A shearspring comprising a disc of elastic plastic material having an openingextending axially therethrough, the wall of said opening having a grooveextending circumierentially therearound, said groove having a crosssectional shape of a parabola, with the depth of the groove given withinapproximately 20% plus or minus by the relation where 111 equals thedepth of the groove, x1 equals one-half the width of the groove and (1equals 0.08521- plus 0.588 with 1- being the radius of the opening atthe point where the groove section is considered.

5. A shear spring comprising a disc of elastic plastic material adaptedto be compressed when placed in service, said dischaving an axialopening therethrough, said spring having a groove in its outerperipheral edge and a groove extending circumierentially around the wall01! said opening. said grooves having a cross sectional contourcorresponding to the shape of a parabola when said disc is free fromcompression, the parabola in each case following within 20% plus orminus-oi the equation where a: is a dimension measured from the medianaxis of the groove, where a equals 0.0852r plus 0.588 with 1' being theradius 0! the disc at the point where the groove is considered, and ydetermines the depth of the groove. 6. A shear spring comprising a discof elastic plastic material adapted to be compressed when placed inservice, said disc having anaxial opening therethrough, said springhaving a groove in its outer peripheral edge and a groove extendingcircumi'erentially around the wall of said opening, said grooves havinga cross sectional contour cor.- responding to the shape of a parabolawhen said disc is free from compression, the depth 111 of the groove ineaohcase being within 20% plus or minus oi the equation where :1 equalsone-half the width of the groove.

and d equals 0.08521- =p1us 0.588 with 1' being the radius of the discat the point where the groove

